The invention relates to a method for the production of a fibrous web from cellulose fibers having absorbing properties in an air-laid process. Moreover, the invention relates to a fibrous web which is produced according to the aforementioned method. Fibrous webs according to the invention should be suitable for the production of hygiene articles, in particular for incontinence articles, disposable diapers, panty liners or sanitary napkins, whereby they essentially serve as absorbing core for the aforementioned hygiene articles. Absorbent liners for food packages are a further use. Further applications in which the use of cellulose fibers is important while avoiding other fibrous material are known to an expert in the field.
The production of fibrous webs from cellulose fibers in air-laid processes in which, unlike in the wet-laid process, the fibers are placed on a conveyor belt in an air current and compacted by press rolls has been known for many years.
Cellulose fibers that can be used for hygiene products include, in particular, so-called “fluff pulp” fibers which are obtained from northern softwood or from American southern pine. The average fiber length of cellulose fibers of this type is about 2.4-2.8 mm. The absorbency of the loosely compacted dry fibers is about 10-12 g liquid per gram fibers. Corresponding data is found in WO 9316228 (Norlander), Table 2, for untreated reference material or in WO 8804704 (Graef), Table 7. It is known to insert further absorbing material into the fiber matrix; in particular, in this connection, so-called superabsorbent polymers (SAP) are known that have an absorbing capacity that is substantially greater than 10 g liquid per gram polymers, which are also produced in a fibrous form (SAF=superabsorbent fibers).
The U.S. Pat. No. 3,692,622describes an absorbent fiber bond in the form of a cellulose fibrous web for producing paper towels, whereby the web is provided with a predetermined embossed pattern. The fibrous web is a continuum of drained, essentially unbound fibers having a length of less than 1.27 cm which are interconnected to form a coherent web by embossings, which cover 5 to 40% of the web surface and have a smaller distance from one another than corresponds to the length of the individual fibers, such that the thickness in the non-embossed areas is at least 2.5 times as great as in the embossed areas.
In fibrous webs which consist exclusively of cellulose fibers, it is a problem to bring the absorbency to a high level and, at the same time, keep the formation of dust low. It is in fact known to produce fibrous webs having fusible synthetic fibers, also so-called bicomponent fibers, and to provide them with a low dust content. However, the partial object of the invention is to dispense with synthetic fiber admixtures of this type. Rather, a fibrous web produced from cellulose fibers should be obtained in which the dust due to fluff, the so-called dust range, is below 0.1% of the starting web. The use of latex binders should thereby be maintained at a low level, i.e. the areal weight in the dry state should be in the range of less than 5 g/m2.